The present invention relates to a shell for bullets of automatic or semiautomatic firearms with inertial closure, particularly for medium- or large-caliber pistols.
Conventional semiautomatic or automatic pistols with inertial closure have a sliding breech which is supported by the frame of the pistol so that it can slide in a direction which is parallel to the axis of the barrel.
Such conventional pistols with inertial closure being of the type having an internally cylindrical stationary barrel with a cylindrical firing chamber for the shell. As is well known in the art, upon firing at the moment when the fired bullet leaves the barrel the shell, if not delayed, moves backwards with the sliding breech thereby to initially outwardly expose a portion of the shell protruding initially outwardly from the chamber of the barrel thereby defining an initially protruding length of the shell.
The magazine with the cartridges is generally accommodated in the butt of the pistol and in each instance one cartridge is moved at the region where the sliding breech operates.
In practice, the sliding breech is movable from a backward position, for allowing the entry of the cartridge transferred from the magazine, to a forward position wherein it closes the firing chamber to the rear. In passing from the backward position to the forward position, the sliding breech engages the cartridge and inserts it in the firing chamber. When it moves in the opposite direction, the sliding breech, by means of an element known as extractor, engages the collar of the shell and removes the shell from the firing chamber, also expelling it through an adapted opening formed laterally or in an upward region in the body of the sliding breech.
The backward movement of the sliding breech is contrasted elastically by a spring, arranged around the barrel, which causes the advancement of the sliding breech.
In these weapons the problem arises of delaying the backward motion of the sliding breech to prevent shell extraction from the firing chamber from beginning before the bullet has left the barrel, i.e., in the presence of very high pressures inside said barrel. If the shell is extracted from the firing chamber whilst the pressure inside said firing chamber is still very high, the shell can burst, causing danger to the user and at the same time jamming the weapon.
Various measures have been adopted to solve this problem.
One of these measures consists in increasing the mass of the sliding breech so that the backward movement of the sliding breech is delayed due to the high inertia caused by its increased mass.
This measure entails some drawbacks, since it increases the weapon weight; moreover, oscillations of the weapon induced by the movement of the sliding breech at the end of its forward and backward movement are observed. These oscillations and the considerable weight of the weapon negatively affect firing precision and the oscillations of the weapon cause the user to lose his line of fire during closely spaced repeat firing.
Another measure consists in forming the moving barrel together with the sliding breech. In practice, during firing the barrel retracts rigidly with the sliding breech by a first extent, so that the sliding breech keeps the firing chamber closed, and then releases the sliding breech so that it ends its backward movement, extracting and expelling the shell.
This measure, too, is not free from drawbacks, since it complicates the structure of the pistol and also increases its production costs. Moreover, the coupling between the barrel and the frame of the pistol and between the barrel and the sliding breech must be performed with considerable play in order to allow the various movements, and these plays inevitably affect the precision of the weapon. In order to obviate this drawback, it is often necessary to manually modify the weapon with highly specialized operations that entail very high costs.
Another measure consists in using the gases produced during firing inside the firing chamber or the barrel, providing an adapted duct with an inlet located in the firing chamber or almost at the end of the barrel in order to deactivate an element which temporarily locks the sliding breech.
This measure considerably affects the production cost of the pistol and reduces the reliability of the weapon, since the gas conveyance duct can clog after a certain number of shots, thus jamming the weapon. The flow of the gases also generates turbulence which reduces the weapon precision.